A new mathematical equation relating activation energy to bond angle and distance: A key for understanding the role of acceleration in lactonization of the trimethyl lock system

2009 ◽  
Vol 37 (1) ◽  
pp. 11-25 ◽  
Author(s):  
Rafik Karaman
Keyword(s):  
Activation Energy ◽  
Bond Angle ◽  
Mathematical Equation ◽  
Trimethyl Lock

scholarly journals The Activating Effect of Strong Acid for Pd-Catalyzed Directed C–H Activation by Concerted Metalation-Deprotonation Mechanism

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4083
Author(s):  
Heming Jiang ◽  
Tian-Yu Sun
Keyword(s):  
Activation Energy ◽  
Dft Calculations ◽  
Energy Barrier ◽  
Computational Study ◽  
Strong Acid ◽  
Activation Energy Barrier ◽  
Pd Catalysts ◽  
Acid Ligand ◽  
Strong Acids

A computational study on the origin of the activating effect for Pd-catalyzed directed C–H activation by the concerted metalation-deprotonation (CMD) mechanism is conducted. DFT calculations indicate that strong acids can make Pd catalysts coordinate with directing groups (DGs) of the substrates more strongly and lower the C–H activation energy barrier. For the CMD mechanism, the electrophilicity of the Pd center and the basicity of the corresponding acid ligand for deprotonating the C–H bond are vital to the overall C–H activation energy barrier. Furthermore, this rule might disclose the role of some additives for C–H activation.

Insights into the synergistic role of metal–lattice oxygen site pairs in four-centered C–H bond activation of methane: the case of CuO

2016 ◽  
Vol 6 (11) ◽  
pp. 3984-3996 ◽  
Author(s):  
Jithin John Varghese ◽  
Quang Thang Trinh ◽  
Samir H. Mushrif
Keyword(s):  
Activation Energy ◽  
Copper Oxide ◽  
Bond Activation ◽  
Lattice Oxygen ◽  
Oxide Surfaces ◽  
Energy Barriers ◽  
Metal Lattice ◽  
Oxygen Site ◽  
Site Pair

Of the three mechanisms for activation of methane on copper and copper oxide surfaces, the under-coordinated Cu–O site pair mediated mechanism on CuO surfaces has the lowest activation energy barriers.

scholarly journals Kinetic Analysis of the Effect of Poliovirus Receptor on Viral Uncoating: the Receptor as a Catalyst

2001 ◽  
Vol 75 (11) ◽  
pp. 4984-4989 ◽  
Author(s):  
Simon K. Tsang ◽  
Brian M. McDermott ◽  
Vincent R. Racaniello ◽  
James M. Hogle
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Kinetic Analysis ◽  
Transition State Theory ◽  
State Theory ◽  
Viral Receptor ◽  
Poliovirus Receptor ◽  
Entropic Stabilization ◽  
Entropic Effects

ABSTRACT We examined the role of soluble poliovirus receptor on the transition of native poliovirus (160S or N particle) to an infectious intermediate (135S or A particle). The viral receptor behaves as a classic transition state theory catalyst, facilitating the N-to-A conversion by lowering the activation energy for the process by 50 kcal/mol. In contrast to earlier studies which demonstrated that capsid-binding drugs inhibit thermally mediated N-to-A conversion through entropic stabilization alone, capsid-binding drugs are shown to inhibit receptor-mediated N-to-A conversion through a combination of enthalpic and entropic effects.

scholarly journals Unexpected Role of Electronic Coupling between Host Redox Centers in Transport Kinetics of Lithium Ions in Olivine Phosphate Materials

2021 ◽  
Author(s):  
Yu Gao ◽  
Jun Huang ◽  
Yuwen Liu ◽  
Shengli Chen
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Lithium Ion ◽  
Transport Kinetics ◽  
Electronic Coupling ◽  
Lithium Ions ◽  
Kinetics Of ◽  
Olivine Phosphate ◽  
Redox Centers

The discrepancy between the trend in the diffusion coefficient of lithium ion (DLi+) and that in the activation energy of ion hopping signals hidden factors determining ion transport kinetics in...

scholarly journals Influence of sodium carbonate addition on weight loss of bagasse alkaline black liquor during pyrolysis

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 2428-2441
Author(s):  
Xusheng Li ◽  
Jinlong Wang ◽  
Derong Yan ◽  
Yongjun Yin ◽  
Shuangfei Wang
Keyword(s):  
Activation Energy ◽  
Weight Loss ◽  
Sodium Carbonate ◽  
Black Liquor ◽  
Reduction Reaction ◽  
Loss Ratio ◽  
N2 Atmosphere ◽  
Microscopic Morphology ◽  
Weight Loss Ratio

To understand the effects and the mechanism of sodium carbonate (Na2CO3) addition on the bagasse alkaline black liquor (BABL) pyrolysis, the reaction variables such as temperature, heating rate, and amount of Na2CO3 addition into BABL-solids were investigated under N2 atmosphere from 50 °C to 1000 °C by thermogravimetic analysis (TGA). Scanning electron microscopy (SEM) and the Coats–Redfern method (CRM) were employed for surface microscopic morphology observations and kinetic analysis, respectively. The results showed that Na2CO3 plays an inhibiting and promoting role during devolatilization (200 °C to 650 °C) and the reduction stages (650 °C to 1000 °C), respectively. Adding Na2CO3 into BABL-solids tends to increase the thickness of the salt layer covering the BABL-solids surface, which increases the activation energy and reduces the weight loss ratio of BABL-solids pyrolysis within 200 °C to 650 °C. Adding Na2CO3 into the BABL-solids tends to increase the number of alkaline compounds or the active site of the reduction reaction, which reduces the activation energy and increases the weight loss ratio of BABL-solids pyrolysis within 650 °C to 1000 °C. The role of Na2CO3 as an additive could be well understood by studying the influence mechanism of Na2CO3 on BABL-solids pyrolysis.

Effects of Acyl Chain Unsaturation on Activation Energy of Water Permeability across Droplet Bilayers of Homologous Monoglycerides: Role of Cholesterol

Langmuir ◽  
2018 ◽  
Vol 34 (5) ◽  
pp. 2147-2157 ◽  
Author(s):  
Maria Lopez ◽  
Jacqueline Denver ◽  
Sue Ellen Evangelista ◽  
Alessandra Armetta ◽  
Gabriella Di Domizio ◽  
...  
Keyword(s):  
Activation Energy ◽  
Water Permeability ◽  
Acyl Chain

Flow of nanofluid towards a Riga surface with heat and mass transfer under the effects of activation energy and thermal radiation

2021 ◽  
pp. 2150266
Author(s):  
A. Al-Zubaidi ◽  
Mubbashar Nazeer ◽  
S. Saleem ◽  
Farooq Hussain ◽  
Fayyaz Ahmad
Keyword(s):  
Activation Energy ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Porous Medium ◽  
Shooting Technique ◽  
Highly Nonlinear ◽  
Riga Plate ◽  
Buongiorno Model ◽  
Momentum Boundary Layer

This paper numerically simulates the nanofluid flow over a thermally expanding Riga plate. Buongiorno model for nanofluid is employed to investigate the contribution of Brownian motion and thermophoretic force on the nanoflow. Magnetohydrodynamics (MHD) of viscous nanofluid through a porous medium is characterized with the help of Darcy–Forchheimer’s model. In addition, the simultaneous effects of activation energy and chemical reaction have been incorporated. Moreover, highly nonlinear coupled differential equations are formulated which highlight the influence of viscous dissipation and heat generation. A numerical solution is achieved with the help of the Range–Kutta fourth-order (RK4) method combined with the shooting technique. Finally, the role of emerging parameters is studied via performing the numerical simulation which reveals that the momentum boundary layer of nanofluid shrinks due to the porous medium. Whereas, thermal boundary layer expands for all variables, except for the Prandtl number. Finally, mass transfer rated suffers due to Schmidt number.

Relevance of the Entropy Factor in Stereoselectivity Control of Asymmetric Photoreactions

Synlett ◽  
2020 ◽  
Vol 31 (13) ◽  
pp. 1259-1267
Author(s):  
Tadashi Mori
Keyword(s):  
Activation Energy ◽  
Excited States ◽  
Weak Interactions ◽  
Supramolecular Interactions ◽  
Thermal Reactions ◽  
Thermodynamics And Kinetics ◽  
Control Concept ◽  
Entropy Factor ◽  
Fine Tune

Entropy as well as enthalpy factors play substantial roles in various chemical phenomena such as equilibrium and reactions. However, the entropy factors are frequently underestimated in most instances, particularly in synthetic chemistry. In reality, the entropy factor can be in competition with the enthalpy factor or can even be decisive in determining the overall free or activation energy change upon molecular interaction and chemical transformation, particularly where weak interactions in ground and/or excited states are significant. In this account, we overview the importance of the entropy factor in various chemical phenomena in both thermodynamics and kinetics and in the ground and excited states. It is immediately apparent that many diastereo- and enantioselective photoreactions are entropy-controlled. Recent advances on the entropy-control concept in asymmetric photoreactions are further discussed. Understanding the entropy-control concept will pave the way to improve, fine-tune, and even invert the chemo- and stereoselectivity of relevant chemical phenomena.1 Introduction2 Role of Entropy in Supramolecular Interactions3 Selected Examples of Entropy-Driven Thermal Reactions4 Classical Examples of Entropy Control in Photoreactions5 Entropy-Driven Asymmetric Photoreactions6 Advances in Entropy Control7 Perspective

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